This application claims priority under 35 U.S.C xc2xa7365(c) to international patent application PCT/GB99/03350 filed Oct. 8, 1999, which in turn claims priority to United Kingdom patent application 9822152.6 filed Oct. 12, 1998 and United Kingdom patent application 9913584.0 filed Jun. 14, 1999, the entire disclosures of which are incorporated herein by reference.
This invention relates to a pumping apparatus and more particularly to a pumping apparatus for pumping lubricant in an internal combustion engine, and to a sump and an engine incorporating such a pumping apparatus.
In an internal combustion engine it is common practice to provide a lubricant pump which is operative to pump lubricant, usually oil, to parts of the engine which require lubrication. The oil drains back to a sump under gravity.
Known such pumps are driven by a mechanical coupling with a driven part of the engine, such as from a gear or cam carried by e.g. the camshaft or crankshaft of the engine. Thus the choice of positions at which the oil pump must be sited, is restricted by the nature of the mechanical coupling. The pump is only driven when the driven part of the engine moves, i.e. when the engine is running.
As a result, during start-up of an engine particularly from cold, there is a short period before an adequate supply of oil is delivered to the engine parts which require lubrication. Thus during start-up, the engine is particularly prone to wear.
Also in modern engines which incorporate parts which rotate at high speed, such as the rotor of a turbocharger, such rotating parts tend to continue to rotate for some time after the engine is switched off and the driven part of the engine from which the oil pump is driven, stops moving. Thus such rotating parts tend to be inadequately lubricated when the engine is switched off and wear is aggravated as such rotation results in a temperature rise due to the cessation of force fed lubrication, which acts as a heat transfer means.
Another problem with conventional oil pumps is the necessity to provide pipework for a supply of oil to and delivery of oil from the oil pump, which can be complicated by the position at which the oil pump is mounted being governed by the mechanical coupling to the driven part of the engine.
Yet another problem with conventional oil pumps which are driven by a driven part of the engine is the inability to control the speed of the pump other than as a result of engine speed. Particularly, as engine speed increases, so will the oil flow delivered by the pump. At high engine speeds, it would be preferable to limit the oil pump speed for the most efficient lubrication of the engine, and to limit wear on the oil pump itself.
It is well known to drive a pump using an electric motor but this has not been adopted generally in an engine environment for several reasons. First, there are the economic considerations of providing a motor driven pump. Second, a motor would generate heat and would itself require cooling.
According to a first aspect of the invention we provide an apparatus for pumping lubricant in an internal combustion engine, the apparatus including a lubrication pump for pumping the lubricant, and electric motor means for driving the pump, the lubricant being pumped from a reservoir in which at least the lubrication pump is immersed, and characterised in that the motor includes a stator and a rotatable motive member, the stator and rotatable motive member of the motor means being in contact with lubricant from the reservoir.
Thus the temperature of the motor may be stabilised by the lubricant in contact with it, and furthermore, the motive member and/or bearings carrying the motive member may readily be lubricated. Because the pump is driven by a motor and not a mechanical coupling from a driven part of the engine or other machine, there is less restriction on the positioning of the pump compared with conventional arrangements.
Thus the potential technical problems of using a motor driven pump e.g. for pumping lubricant in an internal combustion engine or other machine, may be overcome. Even though a motor driven pump may be more expensive than a conventional pump driven e.g. from a driven part of the engine, the benefits achieved may offset this extra cost.
Amongst the advantages of providing a pumping apparatus in accordance with the invention in such an environment arc that the speed of the pump may be controlled because the pump is not mechanically coupled to a driven part of the engine; the pump may be actuated independently of the engine and thus may pump lubricant prior to start-up and subsequent to switching off the engine so that the engine is less prone to wear during such periods; the performance of the motor/pump may be used as a diagnostic tool for diagnosing a) engine malfunctions such as for example a blockage in a lubrication passageway, and b) engine wear which tends to result in an increased requirement for lubricant to be pumped.
Preferably the reservoir in which at least the lubricant pump is immersed, is a sump of the engine from which lubricant is pumped to moving parts of the engine.
In one embodiment, the pump and the motor means are arranged with the pump and the motor means immersed in lubricant in the reservoir. Thus the motor need not have a housing or other outer casing. In another embodiment where the pump only is immersed in the lubricant, the motor means may include a motor housing with one or more passages for the lubricant e.g. from the pump, to the interior of the motor housing. In each case by virtue of the pump and/or pump and motor means being immersed in the fluid in the sump, the temperature of the motor means and the pump will be stabilised by the fluid and will realise the temperature of the lubricant.
By providing a pump or pump and motor means which are positioned in the sump, there is no need to provide pipework to the pump for the fluid to be pumped. Preferably, the pump is connected to a remote filter which filters the fluid e.g. prior to the lubricant being directed to moving parts of the engine.
In a preferred arrangement, the fluid to be pumped may be pumped by the pump through a heat exchanger where the lubricant is cooled by a coolant in thermal contact therewith. The coolant may be for example only, water or another coolant which may be predominantly water or the like.
Preferably the heat exchanger is located closely adjacent to a housing of the pump exteriorly of the reservoir, e.g. in the air, so that the air may perform some cooling of the fluid. Where the pump pumps fluid from the sump to a filter, a fluid outlet from the heat exchanger may be connected directly to a housing in which the filter is provided or the filter housing may be integral with the or a housing of the apparatus.
The motor is preferably an electric motor in which case there may be provided a control means for the motor. The control means may be of an electronic nature, the temperature of which may need to be retained below a threshold level. Most conveniently the control means is positioned at least adjacent the pump so that there is no need for there to be long leads between the control means and the motor. Where there is provided a heat exchanger through which a coolant flows to cool the fluid to be pumped, the control means may too be cooled by the coolant. For example the control means may be contained in a housing in thermal contact with the heat exchanger.
The control means may be adapted operatively to be connected to a management system controlling an engine or other machine in which the fluid is to be pumped.
In another embodiment the motor is an electric motor having external stator windings and an internal rotor, the internal rotor includes an axially extending opening with generally radially inwardly formations such as gear-like teeth, and the pump includes an impeller which is received in the axially extending opening, the impeller having generally radially outwardly extending formations such as gear-like teeth, which co-operate with the radially inwardly extending formations of the rotor so that the impeller is driven as the rotor rotates, the radially outwardly extending formations of the impeller pumping the fluid as the impeller is rotated.
Thus the impeller and motor may be integrated substantially to reduce the axial extent of the apparatus compared with an apparatus in which an impeller is connected at an axial end of a motor rotor or other rotatable motive member of the motor. Thus a more efficient design may be achieved with inherent reductions in manufacturing cost and time. The overall size and mass of the apparatus may be lower than that of a comparable apparatus with non-integrated motor and pump elements.
In a preferred arrangement of this alternative embodiment, the impeller may rotate in the axially extending opening of the internal rotor about an axis which is parallel to but spaced from an axis about which the internal rotor rotates whereby in use, at any time, only some of the co-operating formations of the internal rotor and the impeller are in co-operation, and a pumping cavity for fluid to be pumped, is provided between the internal rotor and the impeller.
According to a second aspect of the invention we provide an internal combustion engine having a sump for lubricant to be pumped, and an apparatus according to the first aspect of the invention to pump the lubricant in the engine.
The engine is preferably provided with a management system which may interface with a control means of the apparatus, which is operative to control the motor speed, the management system and control means controlling pump speed according to engine operating conditions.
According to a fourth aspect of the invention we provide a method of operating an engine of the third aspect of the invention the method including actuating the pumping apparatus prior to start-up of the engine and/or subsequent to switching off of the engine.
According to a fifth aspect of the invention we provide a method of performing diagnosis of an engine malfunction including providing to an engine management system, an input from a control means of an electric motor of pumping apparatus of the first aspect of the invention.